Pneumatic tires for off-road vehicles incorporate a tread designed to provide high traction in non-paved surfaces, such as soft earth or ground, frequently encountered by earthmoving equipment, agricultural vehicles, sport utility vehicles, military vehicles, lawn and garden vehicles, all-terrain vehicles (ATV's), and dirt bikes. Frequently, pneumatic tires for off-road applications have low operating pressures and minimal belt reinforcements. For example, ATV tires generally operate at a pressure of less than 5 pounds per square inch (psi) and frequently lack any belt reinforcing structure.
Pneumatic off-road tires are prone to sidewall punctures resulting in a loss of tire pressure or deflation. Sidewall punctures arise from penetrating or sharp objects such as rocks, thorns, sticks, stubble, or bushes, in the surrounding environment that contact and penetrate the sidewall causing the tire to lose tire pressure either quickly or gradually. The sidewall punctures may be manifested as perforations or slits affording an escape route for the pressurized fluid filling the tire. The occurrence of sidewall punctures is unpredictable and, typically, off-road vehicles carry a repair kit or a spare tire in anticipation of such an event. Repair kits are inconvenient to carry and, although simple perforations can be repaired using the repair kit, large perforations and slits are, at the least, more difficult to repair. In addition, repairs made using the repair kit may be time consuming and, in many conditions such as mud, snow, and uneven rocky terrain, may be challenging to perform. If a spare tire is unavailable or the repair kit is ineffective for repairing the sidewall puncture, the vehicle occupants, such as farmers, hunters, fishing enthusiasts and recreational ATV riders, must travel by foot from a remote location over potentially difficult terrain to obtain assistance.
Thickening the sidewall may reduce the likelihood that a sharp object can puncture the sidewall of an off-road tire. Conventional approaches for thickening the sidewall include either adding material in the form of additional plies or an increased rubber thickness. In particular, conventional run-flat or tires have been developed that incorporate relatively thick sidewalls having an increased rigidity capable of carrying the full vehicle load in the absence of inflation pressure. Due to the enhanced sidewall thickness, run-flat tires also provide tremendous puncture resistance. However, such conventional solutions do significantly increase the cost of manufacturing the off-road tire, which is ultimately transferred to the consumer in the retail price.
Pneumatic off-road tires may include a single, circumferential scuff rib that projects outwardly from the sidewall. Typically, the scuff rib provides resistance to sidewall scuffing arising from the abrasive effects of recurring contact between the tire sidewall and immovable objects, such as a curb or the like. The scuff rib typically extends from a planar outer surface toward the sidewall at an angle greater than about 45° measured relative to a base surface of the sidewall. However, the scuff rib can only assist in preventing sidewall punctures from sharp objects over the portion of the base surface actually covered by the scuff rib. The scuff rib cannot provide puncture resistance to sharp objects over the exposed base surface of the sidewall, which represents the greater part of the sidewall surface area.
For these and other reasons, it would be desirable to provide a pneumatic off-road tire having an improved sidewall puncture resistance while thickness of protective material incorporated into the sidewall.